"First, our communities expose us to disproportionate support for our 
own ideas.  Second, they shield us from the disagreement of 
outsiders.  Third, they cause us to disregard whatever outside 
disagreement we encounter.  Finally, they squash the development of 
disagreement from within.  These factors create a kind of societal 
counterpart to cognition's confirmation bias, and they provoke the 
same problem.  Whatever the other virtues of our communities, they 
are dangerously effective at bolstering our conviction that we are 
right and shielding us from the possibility that we are wrong."

Kathryn Schultz, Being Wrong, 2010.  HarperCollins, p 149.

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